A variety of flame retardant compounds are available as articles of commerce. Despite extensive research over the years, the art still continues to search for new aromatic hydrocarbons which can be readily brominated to produce highly effective brominated aromatic flame retardants. Some of the latest developments in the art involve new process technology for bromination of linear styrenic polymers formed by anionically-initiated polymerization of styrene.
This invention is believed to provide new technology for producing branched and/or star-branched styrene polymers or telomers or adducts anionically and via chain transfer, which polymers or telomers or adducts, on bromination, will provide the art with novel, highly-effective brominated aromatic flame retardants.
In connection with products of this invention and terminology used anywhere in this document, including the claims:    1) the term “styrene polymer”, whether in the singular or plural, denotes styrene branched and/or star-branched addition product(s) having degrees of polymerization in the range of greater than about 0.85 and having greater than about 10 GPC area % of the molecular weight distribution having an Mw greater than 620 Daltons; and    2) the term “styrene telomer”, whether in the singular or plural, denotes styrene branched and/or star-branched addition product(s) having degrees of polymerization in the range of about 0 to about 1.1 and having less than about 10 GPC area % of the molecular weight distribution having an Mw greater than 620 Daltons; and    3) the term “styrene adduct”, whether in the singular or plural, denotes styrene branched and/or star-branched addition product(s) having degrees of polymerization equal to 0. That is to say there are no styrene repeat units present in the distribution.The value of “degrees of polymerization” can be satisfactorily estimated by calculating as if the material was a linear polymer. The calculation is, therefore, a reasonable approximation. For a polymer in which a xylene, a trimethylbenzene, or a tetramethylbenzene is the chain transfer agent(s) (hereinafter referred to in the singular or plural as CTA), the respective number average degrees of polymerization (DP) are calculated from the Mn, or weighted averages thereof, of the particular product distribution according to the equations:DPxylene=(Mn−210)/104DPtrimethylbenzene=(Mn−224)/104DPtetramethylbenzene=(Mn−238)/104
In each case, the above polymers or telomers or adducts are produced by controlled reactions involving both anionic initiation and chain transfer.